1. Field of the Invention
This invention releates to an optically active alkyl or alkoxy benzoic acid alkyl or alkoxyphenyl ester compound which is useful as a ferroelectric liquid crystal compound.
2. Description of the Prior Art
Methods of displaying with a liquid crystal display element widely used today may be classified into those of twisted nematic (TN) and dynamic scattering (DS) types. These methods involve nematic liquid crystals cells comprising nematic liquid crystals as the main component. One of the disadvantages of conventional nematic liquid crystal cells is that their response speed is of the order of several milliseconds at the most, which considerably restrict the application thereof. It has been recently found that a higher response speed can be obtained by using a smectic liquid crystal cell.
It has been disclosed that some optically active smectic liquid crystals show ferroelectricity and thus the application thereof has been eagerly expected. An example of the ferroelectric liquid crystals is 2-methylbutyl 4-(4-n-decyloxybenzylidenamino)-cinnamate which will be abbreviated to DOBAMBC hereinafter. This compound is characterized by showing a ferroelectricity in the chiral smectic phase which will be abbreviated to Sc* phase hereinafter.
Since it was found that a DOBAMBC film cell had a high response speed of the order of a microsecond, this ferroelectric liquid crystal compound has attracted public attention as a material available not only in display devices of, for example, a liquid crystal TV but also in various optoelectronics devices such as a photoprinter head, an optical Fourier-transform element and a light valve.
However the DOBAMBC has not been utilized in practice yet, since it is chemically unstable because of the presence of a Schiff base structure therein.